I dont often participate in BRs or Public BRs, however it is a struggle as a criminal organisation to plan a BankRob accordingly. Especially with the current Police activity. To further reduce the robbery options on the bank by increasing the minimum spawned officer for a Public BR doesn't seem like the right plan in this case.
Instead of trying to increase the minimum amount of cops needed for these activities, we as a whole, should focus on increasing the activity on the Policing side of the server. Some are already working on this by creating thier own squad. Some people are capable of being a police officer, but are not included in a "Official Squad" & hence do not count towards this (Public) BR number.
Perhaps we could get some groups involved like SAi, PC, etc. ( Quick idea ) Not all of the members there may be part of a official Squad, but it could help towards the activities around a BankRob/Public BR or U name it.
To further raise the Police activity, some further actions should be considered. Open for discussion.